32 
MAMMALIA. 
oily fat. Their blood is warm. Their cerebral hemispheres are 
highly developed, and folded in numerous circumvolutions. 
Such are the principal characteristic features of the Mammalia 
which compose the order of Cetacea. 
The largest of other animals are small when compared with 
many of the Cetacea ; these colossal creatures, however, swim 
with more or less rapidity. In consequence of the air contained 
in their chest, the great quantity of grease with which their tissues 
are charged, and the vigour of their caudal flukes, they move 
easily through the waves, looking with voracity for fish, molluscs, 
and Crustacea, of which they consume an enormous quantity. 
Whaling for these great Cetacea involves very important 
nautical expeditions, and furnishes the raw material for the manu- 
facture of animal oils, elastic fibres, and some ivory. 
This order is divided into two principal families, which are 
distinguished by the food they eat, by their teeth, and, above all, 
by the position of their nostrils. These are the ordinary or blowing 
Cetacea and the herbivorous Cetacea. These two families comprise 
a very great number of species, nearly all of which are marine.* 
Family of Blowing, or Spouting Cetacea. — The blowing 
Cetacea have their nostrils pierced on the upper surface of the 
head, and their nasal cavities present a peculiar arrangement, which 
allows these animals to appear to throw up a column of water above 
their head. The narrow opening of the blowing Cetacea has 
received the name of spiracle or blow-hole. Their mammae are 
placed near the termination of their bodies. Their teeth, when 
they have any, are pointed ; but in some cases the teeth are 
replaced by a very peculiar apparatus, of which we shall speak 
presently. These animals are carnivorous. 
The family of blowing Cetacea, or ordinary Cetacea, is divided 
into two tribes, which are easily distinguished by the relative size 
of the head : the tribe of Whales ( Balcena ), in which the head 
constitutes in itself one-fourth or even one-third of the total 
length of the creature, and ’that of the Dolphins, in which the 
head is in the usual proportion to the body. 
* Professor Owen has shown that the so-called herbivorous Cetacea are more 
nearly related by true affinity to the order Pachydermata , and most naturalists now 
regard them as constituting a peculiar order, which was named Syrenia by the late 
Professor de Blainville. — E d. 
